Investigators are still at work: Did Roper drive voluntarily on little sleep, or did the job demand it? In an industry that pays most truckers based on how far, and how fast, they drive, weary drivers are a too-common danger.

But if drivers work fewer hours, employers must hire more of them to cover the same distance. So the trucking industry fought the sleep rules, and last week a Senate committee voted to start rolling them back.

Efforts to overturn federal sleep rules should be reversed, with more emphasis instead on technology and enforcement to ensure they’re followed. In the long term, the trucking industry needs a reformed pay model, with no financial incentive to drive rather than sleep.

In 2003, New Jersey’s prescient Maggie’s Law put criminal responsibility on drowsy drivers who kill. But a system that pays better for unsafe behavior bears responsibility, too. Wal-Mart has promised to be accountable for Saturday’s crash. The company, whose drivers covered 667 million miles last year, and the entire trucking industry should work to preserve, not overturn, rules that make the highways safer.